Objective      To study the potential roles of γ-aminobutyric acid(GABA) type A receptor (GABA

A

R) agonist and antagonist in mouse placentation.       Methods      Immunohistochemistry was applied to detect the expression of the π subunit of GABA

A

R (GABRP) in the placentas of mid and late phase during mouse pregnancy. Kunming pregnant mice were divided into 8 groups (

n=3) randomly

including 3 treatment groups with daily intraperitoneal injection of GABA

A

R agonist of 0.009 5

0.095

and 0.95 mg/kg separately from D7 to D13

3 treatment groups with daily intraperitoneal injection of GABA

A

R antagonist of 0.018 4

0.184

and 1.84 mg/kg separately from D7 to D13

a control group with injection of saline solution

and a blank group without any treatment. The weights of embryos and placentas were measured and the structure of placenta was observed by HE staining on D14. Besides

the state of proliferation and vasculogenesis in the placenta were evaluated by the expression levels of proliferating cell nuclear antigen (PCNA) and vascular endothelial growth factor (VEGF) using immunohistochemical assay.       Results      GABRP was mainly expressed in the decidua basalis of the uterus from D10 to D17 in pregnant rats. The numbers of blood vessels in the placental decidual zone and nucleated red cells in the labyrinth were significantly increased in the 0.95 mg/kg GABA

A

R agonist group (

P

0.05)

while the expression of PCNA and VEGF was also significantly increased in the placenta labyrinth (

P

0.05). Surprisingly

the weights of placenta and embryo were significantly decreased in the 1.84 mg/kg GABA

A

R antagonist group as compared to the control group (

P

0.05)

while the expression of PCNA and VEGF was reduced in the placenta labyrinth.       Conclusion      GABA may participate in mouse placentation and vasculogenesis via GABA

A

R.